Method for forming flame-retardant clay-polyolefin composites

ABSTRACT

A method for forming polyolefin/clay composites by olefin polymerization which can be used as flame retardants in which at least one filler is combined with an early or late transition metal first catalyst component that becomes activated for olefin polymerization when in contact with the treated filler. An olefin is contacted by the activated catalyst—filler combination either (a) in the absence of an alkylaluminum second catalyst component or (b) in the presence an alkylaluminum second catalyst component when the first catalyst component is an early transition metal catalyst, whereby to form an clay-polyolefin composite incorporating platelets of said filler. The filler is preferably clay, exemplified by montmorillonite and chlorite. The first catalyst component is preferably a non-metallocene catalyst. A predetermined amount of one or more olefinic polymers can also be blended with a masterbatch to obtain a composite having a desired amount of loading.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 11/451,199, filed Jun. 12, 2006.

FIELD OF INVENTION

The invention relates to the formation of flame-retardantclay-polyolefin composites, and more particularly, to the formation offlame-retardant clay-polyolefin composites using non-metallocenecatalysts.

BACKGROUND OF THE INVENTION

Nanocomposites are materials containing two or more chemicallydissimilar phases in which at least one of the phases has a nanoscaledimension. Nanocomposites consisting of exfoliated clay lamellaedispersed in an organic polymer matrix exhibit enhanced physicalproperties relative to virgin polymer, or to conventional macro- ormicrocomposites containing other inorganic fillers (e.g., glass fiber,talc, mica, carbon black) [1]. The enhancements may include improvedtensile and flexural properties, increased storage modulus, increasedheat distortion temperature, decreased flammability [32], decreased gaspermeability, reduced visual defects and improved optical transparency[2].

The clay filler achieves these improvements at very low clay loadings(≦5 wt %), thus the material retains desirable polymer properties suchas light weight, low cost, solution/melt processability andrecyclability. Uses for these nanocomposite materials include moldedautomotive and appliance components (such as body panels, under hoodcomponents, electrical/electronic parts and insulation, power toolhousings) and furniture (such as seat components, consoles), medicaltubing, abrasion and chemical resistant coatings, food packagingmaterials (such as transparent stretch films) and barrier layers forbeverage bottles.

Clays such as kaolinite, hectorite and montmorillonite (MMT) have beeninvestigated as mechanical supports for single-site ethylenepolymerization catalysts [3]. Usually the support is also treated withan organoaluminum co-catalyst, such as a trialkylaluminum or analkylaluminoxane, which serves to remove adsorbed water and passivatethe clay surface. It has also been suggested that alkylaluminumcompounds can cause delamination of kaolinite [4]. In general, thecatalyst is adsorbed onto the co-catalyst-modified clay, where it isactivated in situ by the co-catalyst surface layer [5], [6]. Olefinuptake by the supported catalyst results in controlled particle growth,which is a desirable behavior in polymerization reactor engineering.

Supporting metallocene catalysts on clays results in modest activity forethylene polymerization [7], even in the absence of alkylaluminumco-catalysts [8]. However these catalyst systems do not generate highquality nanocomposites; the polyethylene they produce contains smallclumps of unexfoliated clay.

The desirable physical properties of nanocomposites are observed onlywhen clay sheets are highly dispersed in the polyolefin matrix. Thedifficulty in making exfoliated clay-polyolefin nanocompositesoriginates in the immiscibility of strongly associated hydrophilic claysheets and hydrophobic polyolefin chains. In many varieties of clay,clay layers are negatively charged due to isomorphic substitution offramework ions, generally cations. Interlayer cations provide chargecompensation and promote strong interlayer adhesion, which simple mixingwith a polyolefin cannot effectively disrupt.

One strategy to make the components of the nanocomposite compatible isto render the clay hydrophobic, by replacing the interlayer ions withsurfactants such as long chain alkylammonium, imidazolium oralkylphosphonium cations (typically C18). This procedure generates anorganically-modified layered silicate (OMLS). Methods employing an OMLSin the preparation of polyolefin nanocomposites include:

-   -   In situ intercalative polymerization, in which a catalyst        adsorbed onto the OMLS, causes spontaneous delamination upon        addition of monomer. This strategy has been successfully applied        to propylene polymerization using a zirconocene catalyst        supported on methylaluminoxane (MAO)-treated OMLS [9], and to        ethylene polymerization using a Brookhart Pd catalyst supported        on OMLS [10]. The Ziegler catalyst TiCl₄, grafted onto a        hydroxyl-containing surfactant intercalated into MMT, was used        for in situ polymerization of ethylene upon activation with        triethylaluminum [11]. Silica or titania nanoparticles        synthesized in the interlayer spaces of an OMLS by a sol-gel        method were treated with an alkylaluminum and a metallocene to        create a catalyst system for in situ polymerization [12]. In        situ polymerization filling was achieved using MAO-treated clay        and metallocene or constrained geometry catalysts with [13] and        even without [14], [15] surfactant modification of the clay. In        the absence of surfactant, the clay was swollen using an organic        solvent.    -   Solution intercalation, in which high density polyethylene        (HDPE) dissolved in a hot xylene/benzonitrile mixture is stirred        with dispersed OMLS [16];    -   Melt intercalation, in which the OMLS is annealed with polymer        above the softening point of the latter, either statically or        under shear. Since mixing is driven by interactions between the        polymer and the clay, this method typically requires a        compatibilizer consisting of polymers or oligomers modified with        polar sidechains or endgroups. For example, nanocomposite        formation was achieved by melt intercalation of propylene        oligomers with telechelic OH groups, followed by melt-mixing        with unmodified PP [17]. Melt blending of PP and OMLS was        achieved using a twin screw extruder in the presence of maleated        PP (i.e., functionalized with maleic anhydride side chains,        PP-g-MA) as the compatibilizer [18, 19, 20, 21]. A similar        strategy was used to make nanocomposites by melt blending of        PE-g-MA [22], [23] or EPR-g-MA [23] with OMLS. A semifluorinated        surfactant was used to create an OMLS with weaker        clay-surfactant interactions and a greater propensity to        intercalate unmodified PP [24]. A method involving        functionalized surfactants which react to form chemical bonds        with the maleated compatibilizer has been described [25]. Direct        melt intercalation of ammonium-functionalized polypropylene        chains into unmodified MMT was achieved, presumably by direct        cation exchange, without intermediate functionalization of the        clay with surfactant [26].

Recently, the formation of nanocomposites with unmodified clay wasachieved by making the polyolefin component more hydrophilic. In thepresence of the surfactant cetyltrimethylammonium bromide, micellescontaining polystyrene were formed and adsorbed from solution ontodispersed clay [27].

Also recently, nanocomposite materials have been produced by adding anolefin to a suspension of acid-treated layered silicate treated with asolution of a metallocene polymerization catalyst, causing olefinpolymerization to form the nanocomposite polymer [28]. Althoughdescribed in broad encompassing terms, the specific preparationsdescribed by the reference all require the use of a tripropylaluminumco-catalyst added to the slurry formed by mixing4-tetradecylanilinium-exchanged or HCl-treated clay to dry toluene.

A flame retardant is a material that exhibits either a delay in thestart, or a decrease in the rate of propagation, of a fire [30, 31].Organic polymers can be made flame retardant by incorporating a largequantity (ca. 50 wt %) of an inorganic (e.g., Mg(OH)₂) or organic (e.g.,brominated polystyrene) filler. Flame retardant properties may beobtained at much lower filler content with nanocomposites. Potentialuses for flame retardant nanocomposite materials include moldedfurniture, automotive parts (such as body panels, under hood components)and appliance components (such as electrical/electronic parts, powertool housings).

The first report of improved thermal stability in a polymer-claycomposite involved a polymethylmethacrylate (PMMA)—montmorillonite (MMT)clay system. At 10 wt % clay loading, this material exhibits an increaseof 40-50° C. in its thermal decomposition temperature relative to purePMMA [33]. A nanocomposite prepared by sonication of silanol-terminatedpolydimethylsiloxane (PDMS) with montmorillonite (10 wt %) decompose ata temperature 140° C. higher than pure PDMS [34]. An increase in thedecomposition temperature was observed upon melt intercalation ofaliphatic polyimide (PEI-10) into clay [35]. An increase in the thermaldecomposition temperature was observed for organically-modified layersilicate (OMLS) nanocomposites with polypropylene-graft-maleic anhydride(PP-g-MA) [30,37], PP [38], and polystyrene (PS) [39,40], when comparedto their pure polymer counterparts. In particular, thermogravimetricanalysis (TGA) experiments performed under N₂ showed the onsettemperatures for decomposition of polyethylene (PE)/OMLS nanocompositesare approximately 20-30° C. higher than for pure PE [41].

Flammability properties: Cone calorimetry measurements have demonstrateddecreased flammability for many types of polymer-clay nanocomposites.The heat release rate (HRR), especially the peak HRR, is an importantparameter in evaluating fire safety [42,43]. The reduction in HRR andpeak HRR shown by many polymer-clay nanocomposites suggest a decrease intheir flammability relative to the pure polymers. Delaminatedclay-nylon-6 and -nylon-12 nanocomposites, as well as intercalatedclay-PS and —PP nanocomposites, have shown substantial decreases in HRR[44]. Several PP and PP-g-MA nanocomposites also exhibit a reduction inHRR as measured by cone calorimetry [30, 37, 38, 45]. The peak HRR of PEnanocomposites was reduced by 54% [41].

A more severe test of non-flammability is the capacity of a burningmaterial to self-extinguish. Self-extinguishing behavior of PEI-claynanocomposites has been reported [36], however there is no report ofthis behavior in polyolefin-clay nanocomposites. Similarly, no reporthas shown that a polyolefin/clay nanocomposite has achieved a UL94 VOrating, which is a practical flame retardant material according to theUnderwriter's Laboratory's fire test protocol [46].

BRIEF SUMMARY OF THE INVENTION

The present invention provides a flame retardant composite and a methodfor forming flame retardant composite materials containing a filler,which is accomplished with either an early or late transition metalfirst catalyst component, without the use of alkylammonium modifiers toseparate the filler layers, and without the use of an alkylaluminumsecond catalyst component. In other embodiments, an alkylaluminum secondcatalyst component can be used with an early transition metal firstcatalyst component.

The filler is selected from the group consisting of silicates andnon-silicate compounds. The invention proceeds by combining the fillerwith a first catalyst component that becomes activated for olefinpolymerization when in contact with the filler. An olefin is contactedby the activated catalyst—filler combination in the absence of analkylaluminum second catalyst component to form a composite polymercontaining the filler. The first catalyst component can be selected toprovide a high or low melting point polymer. One class of preferredfirst catalyst components used particularly without the need or use ofan alkylaluminum second catalyst component is a non-metallocenecatalyst, most preferably a nickel complex bearing anα-iminocarboxamidato ligand. Another preferred first catalyst component,one that can be used with or without an alkylaluminum second catalystcomponent, is tetrabenzylzirconium.

In a particular embodiment, sufficient silicate is used to constitute atleast 30 weight % of the composite material to prepare a highsilicate-loaded composite masterbatch. A predetermined amount of one ormore polyolefins can then be blended with the masterbatch to obtain acomposite polymer having a desired amount of silicate loading. In thisinvention, the method to prepare a composite by blending the saidmasterbatch with a predetermined amount of polyolefins is defined as the“masterbatch method.”

In specific embodiments, the silicate material is a clay. In a morespecific embodiment, the invention achieves high dispersion ofmontmorillonite clay platelets in a polyethylene or polypropylene matrixby in situ polymerization of ethylene or propylene. The clay may firstbe acid-treated, causing disruption of its layered structure. Theacid-treated clay is then treated with an organic solvent solution of apolymerization catalyst, which contains Ni, an α-iminocarboxamidatoligand and an alkyl ligand. Upon exposure to olefin, a polyolefin matrixis formed in which the embedded clay layers are mostly separated.

In particular embodiments, capped clay can be used to polymerize olefinin the presence or absence of an organoaluminum second catalystcomponent. The capping of the Brønsted acid sites on the clayessentially passivates the clay surface prior to the deposition ofcatalyst.

The invention allows a new flame retardant composite and preparation offlame retardant clay-polyolefin composites which self-extinguish afterignition, and represents a simple, inexpensive, one-pot procedure formaking silicate-polymer composites without the need for time-consumingorganic modification of the filler material or the use of expensivesurfactants. The flame retardant composite in the invention is notlimited to a nanocomposite, and a flame retardant composite is alsoallowed in which the dimension of the dispersed filler is not nano-scalebut micron-scale.

With the invention, the use of organic solvents to swell the clay and/ordissolve the polymer is also greatly reduced or eliminated. There is noneed for compatibilizers, such as maleated polymers, whose lowermolecular weights and lower stability relative to the polyolefincomponent may result in degradation of composite performance [1]. Thecomposite material can be prepared with or without additional addedflame retardants. With late transition metal catalysts, there is no needfor organoaluminum activators or other co-catalyst modification orpassivation of the surface of the layered filler, since the layeredfiller itself serves as catalyst activator. The improvements asdescribed herein lead to higher quality and less expensive flameretardant composite polymers.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing in which:

FIG. 1 is a TGA graph showing decomposition of PE/clay composites inair; and

FIG. 2 shows a table of char tests on PE-clay composites; and

FIG. 3 shows a photograph of char test for PE-clay composites, recorded1:20 min after ignition. Sample numbers correspond to run numbers inFIG. 2; and

FIG. 4 shows a table of char tests on PP-clay composites; and

FIG. 5 shows a photograph of char tests for PP-clay composites preparedby in situ polymerization, recorded 1:50 mins after ignition. Samplenumbers correspond to run numbers in FIG. 4; and

FIG. 6 shows a photograph of char tests for PP-clay composites, recorded3:00 mins after ignition. Sample numbers correspond to run numbers inFIG. 4.

FIG. 7 shows TEM images of a 5.4 wt % LiMMT/PE composite prepared by insitu polymerization; and

FIG. 8 shows TEM images of a 15 wt % LiMMT/PP composite prepared by insitu polymerization; and

FIG. 9 shows an X-ray diffraction pattern of acid-treatedmontmorillonite; and

FIG. 10 shows TEMs of polyethylene-clay composites with (A) 2.6 wt. %clay, (B) 10.6 wt. % clay, and (C) ethylene/1-hexene copolymer with 2.4wt. % clay; and

FIG. 11 shows TEM images of an 11.1 wt % clay-polyethylene compositeproduced with a trimethylaluminum-modified clay.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a flame retardant composite comprised of at leasta polyolefin, a layered filler, selected from the group consisting oflayered silicates and non-silicate compounds, and a component derivedfrom a complex containing a metal ion and a ligand containing aheteroatom (i.e., the said complex itself, or resulting products thatare formed in a process in which the said complex undergoes somechemical reactions), or a complex in which the said complex has theformula MR, where M is an early transition metal, R is an alkyl orsubstituted alkyl ligand, and x is from 3 to 6.

The invention also provides a flame retardant composite comprised of atleast a polyolefin, a layered filler, selected from the group consistingof layered silicates and non-silicate compounds, and an organic compoundthat can form a radical via pyrolysis or other decomposition process.

The invention provides a method for forming flame retardantclay-polyolefin composites by olefin polymerization in the presence of afiller. Highly exfoliated nanocomposites can also be formed as disclosedin U.S. patent application Ser. No. 11,451,199, filed Jun. 12, 2006, theentirety of which is incorporated herein by reference. However,exfoliation is not necessary for the production of flame retardantcomposites of the present invention.

The filler is selected from the group consisting of nonlayered orlayered silicates and non-silicate compounds, and is combined with acatalyst that becomes activated for olefin polymerization when incontact with the filler. The activated catalyst—filler combination isthen contacted with olefin whereby to form a polyolefin compositematerial incorporating platelets of the filler. The polymerization stepcan be accomplished without the use of an alkylaluminum second catalystcomponent. In other embodiments, an alkylaluminum second catalystcomponent may be used with an early transition metal first catalystcomponent.

More particularly, the filler and a late transition metal first catalystcomponent are added to a reactor followed by the addition to the reactorof the olefin. As stated above, in an advantageous departure from theart, the polymerization reaction can be carried out in the absence of analkylaluminum second catalyst component. This allows significant savingsand simplification of the process. Indeed, where the late transitionmetal first catalyst component is a nickel complex bearing anα-iminocarboxamidato ligand, when trimethylaluminum (a second catalystcomponent, present in 60-fold excess relative to the first catalystcomponent) is added as a scavenger to the reactor after addition of thefiller and first catalyst component, reactor fouling occurs. A largerexcess of trimethylaluminum (350-fold relative to catalyst) inhibits thepolymerization. Moreover, when the second catalyst component is added tothe clay prior to the addition of the late transition metal firstcatalyst component, incorporation of the clay into the polymer matrix iscompromised, and the material is obtained is not a highly exfoliatednanocomposite.

In particular embodiments, sufficient layered filler is used toconstitute at least 30 weight % of the composite material, to prepare ahigh loaded composite masterbatch. A predetermined amount of one or moreolefinic polymers can be blended with the masterbatch to obtain acomposite having a desired amount of loading.

As the filler, clay, clay minerals or compounds having a layered crystalstructure of e.g. a hexagonal densely packed-type, antimony-type,CdCl₂-type or Cdl₂-type, may be used. Specific examples of clay, clayminerals and layered compounds useful as fillers include kaolin,bentonite, kibushi clay, gairome clay, allophane, hisingerite,pyrophyllite, talc, a mica group, a montmorillonite group, vermiculite,a chlorite group, palygorskite, kaolinite, nacrite, dickite andhalloysite.

The silicates to be used as a filler in the present invention may besynthesized products or naturally produced minerals. Specific examplesof the silicates include alkaline silicates such as lithium silicate,sodium silicate, and potassium silicate, alkaline earth silicates suchas magnesium silicate, calcium silicate, and barium silicate, metalsilicates such as aluminium silicate, titanium silicate and zirconiumsilicate, and natural silicates such as an olivine group such asforsterite and fayalite, a garnet group such as garnet, a phenacitegroup such as phenacite and willemite, zircon, tricalcium silicate,merrillite, gehlenite, benitoite, beryl, cordierite, a pyroxene groupsuch as enstatite, hypersthene, diopside, spondumene, rhodonite andwollastonite, an amphibole group such as anthophyllite, tremolite andactinolite.

Particularly preferred as fillers are clay or clay minerals, and mostpreferred are montmorillonite and chlorite. Fillers may be used alone orin combination as a mixture of two or more of them. Flame retardantnano-composites can be formed using montmorillonite, whilemicro-composites can be formed using chlorite.

The fillers used in this invention may be acid treated. Further, theymay be used as they are without subjecting them to any treatment, orthey may be treated by ball milling, sieving, acid treatment or the likebefore use. They may be treated to have water added and adsorbed or maybe treated for dehydration by heating before use. They may also betreated to exchange their interlayer cation by organic cation such asonium cations having aliphatic chains. Specific examples of the oniumcations include primary to quaternary ammonium cation and phosphoniumcation. Specific examples of the aliphatic chains are aliphatic chainswhich have 6-20 carbon atoms including hexyl, octyl, 2-ethylhexyl,dodecyl, hexadecyl, octadecyl and the like, also the mixture of themsuch as hydrogenated tallow. Specific examples of the organic cationinclude hexylammonium, octylammonium, 2-ethylhexylammonium,dodecylammonium, trioctylammonium, dioctadecyldimethylammonium,trioctadecylammonium and the like. They may be used alone or incombination as a mixture of two or more of them.

In one embodiment, the filler material is acidified by contacting itwith a Brønsted acid (such as hydrochloric acid, sulfuric acid, or anymaterial which forms a strong acidic aqueous solution). The aciddissolves some of the aluminum present in the clay and thereby partlydisrupts the layered structure.

The acid-treated filler is dispersed with a small quantity of solvent(such as toluene), which can be done by any suitable technique, and canuse mechanical means if desired or needed such as by sonication or byhigh shear mixing or wet ball milling.

As indicated, the first catalyst component is preferably anon-metallocene catalyst. A non-metallocene catalyst is comprised of atransition metal ion and a ligand that does not contain acyclopentadienyl ring. The ligand for the said non-metallocene catalystpreferably contains at least one heteroatom. Preferred heteroatoms arethe atoms in group 15 and/or group 16 in the Periodic Table. In moredetail, nitrogen, oxygen, sulfur, phosphorus, arsenic, and selenium atomare preferred for the heteroatom in the said ligand. There is nolimitation to the transition metal ion as long as the said complex basedon the metal ion has a function to polymerize α-olefins. An earlytransition metal or a late transition metal can be used in thisinvention. A mixture of non-metallocene catalysts can also be used inthis invention.

In a particular embodiment, the first catalyst component is a latetransition metal catalyst, a nickel complex bearing anα-iminocarboxamidato ligand. The acid-treated clay activates latetransition metal catalysts containing α-iminocarboxamidato ligands,i.e., catalysts from the family LNi(R)(S), where L is anα-iminocarboxamidato ligand, R is an alkyl group (e.g., CH₂Ph) and S isan ancillary ligand (e.g., PMe₃) [28].

Most preferably, the nickel catalyst is a complex having the generalformula I, II, III, IV or V:

wherein:

M is Ni, Pt, Pd;

A is a n-allyl, a substituted π-allyl, a π-benzyl, a substitutedπ-benzyl, benzoyl or picolino ligand;

X is N, P or CH;

Y is O, CH₂, or S;

Z is O or S

L is N or P or a structure that is capable of being a neutral twoelectron donor ligand;

L¹ is a neutral monodentate ligand and L² is a monoanionic monodentateligand, or L¹ and L² taken together are a monoanionic bidentate ligand,provided that said monoanionic monodentate ligand or said monoanionicbidentate ligand is capable of adding to said olefin;

B is a bridge connecting covalently an unsaturated carbon and L;

R¹, R², R^(3A) and R^(3B) are the same or different and are eachindependently hydrogen, hydrocarbyl group, or substituted hydrocarbylbearing functional group;

the designation:

is a single or double bond; and

R^(3B) is nothing when B is connected to L by a double bond.

A particularly preferred catalyst is(N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato)Ni(η³-CH₂Ph).

With late transition metal complexes, such as the nickel complex, nosecond catalyst components are required to achieve typicalpolymerization activities of 1000-15,000 kg polyethylene/mol catalyst/hrat 30° C. The filler does not need to be dried, although betteractivities are obtained with filler dried in vacuo for 12 hours at 100°C. In a typical procedure, a solution of 8 μmol of the catalyst intoluene or hexane is stirred with 85 mg of dried filler under a N₂atmosphere. This catalyst suspension can be loaded directly into thereactor, or filtered, washed and resuspended in fresh, dry solvent priorto use. Hereinafter, the case using clay as filler will be explained,because clay is one of the typical fillers.

In other embodiments, early transition metal catalysts can be used asthe first catalyst component to generate composites, where the metalcomponent of the catalyst can be any early transition metal, such astitanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium,molybdenum, tungsten. Any of a variety of alkyl or substituted alkylligands can be used, particularly those which lack alpha-hydrogens, suchas neopentyl, neosilyl, benzyl, adamantyl, which are stable in the formMR_(x) (where M is the metal, R is the alkyl ligand, and x is the numberof alkyl ligands (from 3 to 6, usually 4).

In a preferred embodiment, an alkylaluminum second catalyst componentcan be advantageously used, that is active in olefin polymerization whensupported on clay, in combination with early transition metal firstcatalyst components, as disclosed above. Preferred second catalystcomponents are trialkylaluminum or an alkyaluminoxane. A particularlypreferred second catalyst component is triisobutylaluminum (TIBA). Thesecond catalyst component can be added first to filler to removeadsorbed water and passivate the clay surface. The second catalystcomponent is also able to cap many of the silanol groups on the claysurface, which would otherwise catalyze polymer decomposition anddeactivate early transition metal catalysts.

More extensive and more robust capping of the silanol groups can beachieved by converting them to trimethylsilyl groups to yieldTMS-capped-LiMMT (TMS-clay). This achieved by stirring a suspension ofLiMMT in neat chlorotrimethylsilane for 2 hours under N₂. The volatilescan be removed either under vacuum at 100° C. for 16 hours, or bywashing with fresh solvent. Activities for ethylene and propylenepolymerization remain the same order of magnitude when TMS-LiMMT treatedwith the second catalyst component is substituted for the secondcatalyst component-non-TMS modified LiMMT. Polymerization with TMS-LiMMTand either early or late transition metal first catalyst components canalso proceed without the use of the second catalyst component, althoughactivities are not as high. The clay can also be capped with othersilylating agents or treated with Brønsted bases (e.g., tertiary aminesor phosphines).

When an olefin is contacted with the activated first catalystcomponent—filler combination, the olefin polymerizes to form a compositematerial containing platelets of an acid-treated filler dispersed in thepolyolefin matrix. It is believed that Lewis acid sites, on certainacid-treated layered fillers, activate the catalyst to produce polymerbetween the layers of the layered filler and thereby separate orexfoliate such layers to a greater degree into the developing polymermatrix.

Preferably, the olefin used in the instant invention is selected fromthe group of olefins having from two to ten carbon atoms. Such olefinsinclude, for example, styrene, divinylbenzene, norbornene, ethylene,propylene, hexene, octene, butadiene and mixtures thereof. Thus, thepolymer product of or by way of the instant invention may be, forexample, a polyethylene, a polypropylene, a thermoplastic elastomer, ora synthetic rubber. It is also possible that larger monomers(macromonomers) are formed in situ and incorporated into the polymer.

In a preferred embodiment, the olefin is ethylene or propylene. Inanother preferred embodiment, the olefin is a combination of ethyleneand an α-olefin, e.g., 1-hexene.

Preferably, the weight % of layered filler in the composite material isat least 0.5%. In a preferred embodiment, sufficient silicate is used toconstitute at least 30 weight % of the composite to prepare a highlysilicate-loaded composite masterbatch. A predetermined amount of one ormore olefinic polymers can be blended with the composite masterbatch toobtain a composite material having a desired amount of silicate loading,e.g., from 0.1 to 20 weight %.

In a particularly preferred embodiment, a flame retardant polyethylenecomposite is formed by treating montmorillonite with an alkylaluminumsecond catalyst component, and then with a tetrabenzylzirconium firstcatalyst component, that becomes activated for ethylene polymerizationwhen in contact with the clay, and contacting ethylene with theactivated catalyst—clay combination.

Polymerization of ethylene or copolymerization of ethylene with anα-olefin such as 1-hexene occurs at temperatures from 10 to 70° C.,preferably between 20 and 50° C. Since the polymerization is highlyexothermic, it is desirable to control the temperature with a heatexchanger to prevent overheating and decomposition of the catalyst above70° C. The polymerization can be terminated by exhaustion of monomer, byventing unreacted monomer, or by quenching the reaction with achain-terminating agent, such as hydrogen gas, carbon monoxide or apolar comonomer.

Thermal stability of polyolefin/clay composites: The thermal stabilityof polyethylene (PE)/clay composites was assessed by thermogravimetricanalysis (TGA). The TGA experiments were performed in air as thetemperature was ramped from 25 to 600° C. at a rate of 20° C./min (FIG.1). The onset of decomposition for the composite materials occurs attemperatures similar to that seen for pure PE made using the samecatalyst activated by a homogeneous Lewis acid, B(C₆F₅)₃, in the absenceof clay. The TGA graphs show that aerobic polymer decomposition occursin at least two stages. For pure PE, the first stage is barelydetectable; most of the mass loss occurs in the second stage. For thecomposites, the first stage extends to higher temperatures, resulting inslightly more mass loss for materials with <10 wt % clay, andconsiderably more for materials with >10 wt % clay. The second stage ofdecomposition occurs at substantially higher temperatures for allPE/clay composites, indicating that they are more thermally stable thanpure PE, even at low clay loadings.

Flammability of polyolefin/clay composites: A modified char test wasused to evaluate flammability. Compression-molded bars (60×6×3 mm) wereclamped vertically and ignited at the top with a butane lighter for 7sec. The amount of time required to either self-extinguish or burncompletely was recorded.

The results of char tests with PE/clay composites are summarized in FIG.2, and a photograph of a char test with a variety of TMS-clay-containingPE samples is shown in FIG. 3. Samples 1-5 are composites prepared by insitu polymerization, while samples 7-10 are composite materials made bythe masterbatch blending method. Samples 7-8 were blended from a 52.8 wt% LiMMT/PE masterbatch, sample 9 was made with a 57.0 wt % masterbatchcontaining TIBA-treated TMS-LiMMT, and sample 10 was blended from a 50.8wt. % masterbatch containing only TMS-LiMMT (no TIBA).

All of the PE composites, whether made by in situ polymerization or bythe masterbatch method, resisted ignition compared to PE containing noclay. Materials made by in situ polymerization, with or withoutTMS-capping (samples 1-5), self-extinguished. Samples 1-4 formed char onthe surface of the bar. The formation of char prevents diffusion ofcombustible volatiles that sustain the flame [2]. The material with thelowest clay loading (sample 1) had the shortest self-extinguishing time.However, the blended materials (samples 7-10) burned faster than PEalone (sample 6) and generated a lot of black smoke.

The results of char tests with polypropylene (PP)/clay composites aresummarized in FIG. 4. Representative photographs of the char tests arepresented in FIGS. 5 and 6. Samples 11a and 11b were performed with barsof isotactic PP containing no clay. Two bars with high clay loadings, 20wt % LiMMT/TIBA (sample 12) and 30 wt % TMS-LiMMT (sample 13), were madeby in situ polymerization. Three bars were made by the masterbatchmethod, blended with isotactic PP to 5 wt % clay: sample 14 was blendedfrom a 42.3 wt % LiMMT/TIBA/PP composite; sample 15 was blended from a76.9 wt % TMS-LiMMT/PP composite; and sample 16 was blended from a 35.1wt % TMS-LiMMT/TIBA/PP composite.

After ignition, sample 11a began to melt, causing liquid polymer to dripdown the side. The sample burned continuously for 1:44 min, until theflame reached the base and was extinguished manually. TheLiMMT/TIBA-containing composite (sample 12) did not drip but took onlyslightly longer (2:38 min) for the flame to reach the base, when it wasextinguished manually. On the other hand, the TMS-LiMMT/TIBA/PPcomposite (sample 13) self-extinguished 1:04 min after ignition. At theend of the experiment, char was observed covering the top of bothcomposites formed by in situ polymerization. Capping of the Brønstedacid sites, either by TIBA or TMS, retards catalytic decomposition ofthe polymer to smaller hydrocarbon fragments. The isotactic PP bar(sample 11b) took the shortest time to burn to the bottom of samples 11band 14-16 in FIG. 6.

Unlike the blended PE composites, the blended PP composites showed flameretardant properties. All of the PP-masterbatch blends (samples 14-16)burned slower than PP containing no clay. In addition, the materialcontaining TMS-LiMMT/TIBA self-extinguished after 3:22 min.

As evident from the above, the flame retardant composites can be madedirectly, or using a masterbatch with high clay loading (e.g., >50 wt %)which is subsequently blended with pure polymer (polyethylene,polypropylene, copolymers of ethylene with other α-olefins, etc) tocreate composites with the desired clay loading. The method can be usedfor composites of homopolymers such as ethylene and propylene,copolymers of ethylene with other α-olefins or with functionalizedmonomers such as styrenes or norbornenes.

The following examples will illustrate best practices of the invention.

Example 1

A solution of TIBA (2.0 g of 1.0 M in hexanes), a second catalystcomponent, was added to LiMMT (1.3 g) in 15 g toluene, and a yellowsolution of the air-sensitive first catalyst component, Zr(CH₂Ph)₄ (50mg in 10 g toluene) was mixed with the LiMMT/TIBA slurry for 15 mins at20° C. The slurry was washed twice, by removal of excess solvent,resuspension in 20 g of fresh toluene, and stirring for 15 mins. Afterthe final removal of excess solvent, the slurry was resuspended in 70 gfresh toluene, and placed inside a batch polymerization reactor. Thereactor was pressurized with 100 psi ethylene at 25° C. andprepolymerized for 15 min. The temperature was increased to 40° C. andthe polymerization allowed to proceed for an additional 45 mins. Thereaction yielded 23.9 g of PE with a clay content of 5.4 wt %.

Typical polymerization activities are 150 kg PE/mol catalyst/hr at 40°C. and 30 kg PP/mol catalyst/hr at 50° C. Polymerization of ethylene isconducted between 25 and 60° C., preferably between 40 and 50° C. Sincethe polymerization is highly exothermic, it is desirable to control thereactor temperature with a heat exchanger to prevent overheating anddecomposition of the catalyst above 70° C. Ethylene is added on demandat 100 psi once the temperature is equilibrated. Typical clay loadingafter a 30 min polymerization at 40° C. is 15 wt %. In order to achievea lower clay loading material (<10 wt %), a pre-polymerization step isimplemented. Ethylene is added at 25° C. for 15 min, then thetemperature is raised to 40° C. for 45 min to obtain a 5 wt % PE/claycomposite. Exfoliation of the clay layers is shown in the transmissionelectron microscopy (TEM) images, FIG. 7. Individual clay sheets arevisible in profile as dark lines against the light gray PE background.

Example 2

The procedure of Example 1 can be repeated except that polymerization iscarried out using propylene. Polymerization is conducted between 30 and60° C., preferably between 40 and 50° C. Since the polymerization ishighly exothermic, it is desirable to control the reactor temperaturewith a heat exchanger to prevent overheating and decomposition of thecatalyst above 70° C. Typical clay loading for a 30 min polymerizationat 50° C. is 40 wt %, but loadings as low as 15 wt % have been obtained.Partial exfoliation of the clay layers at 15 wt % loading is shown inthe TEM images in FIG. 8.

Example 3

LiMMT (2.5 g) was suspended in chlorotrimethylsilane (10 mL), andstirred at 20° C. for 2 hours. The volatiles were removed by heating at100° C. under dynamic vacuum (16 hours at ≦10-4 Torr), then the solidwas transferred to a N₂-filled glove box. A solution of TIBA (2.0 g of1.0 M in hexanes) was added to the TMS-capped clay in 15 g hexanes, anda yellow solution of the air-sensitive first catalyst component,Zr(CH₂Ph)₄ (200 mg in 10 g hexanes) was mixed with the TMS-cappedclay/TIBA slurry for 15 mins at 20° C. The slurry was washed twice, byremoval of excess solvent, resuspension in 20 g of fresh hexanes, andstirring for 15 mins. After the final removal of excess solvent, theslurry was resuspended in 70 g fresh hexanes, and placed inside a batchpolymerization reactor, whose temperature was equilibrated at 50° C. Thereactor was pressurized with 140 psi propylene and polymerization wasallowed to proceed for 60 mins. The reaction yielded 8.9 g ofpolypropylene with a clay content of 30 wt %.

Example 5

PP/clay composites prepared by the masterbatch blending method are flameretardant materials. The masterbatch was made using the method describedabove for the PP/LiMMT composite, but with a TMS-clay treated with TIBAand 30 min polymerization time. A physical mixture of the 35.1 wt %TMS-clay-TIBA/PP composite (0.57 g) and pure PP (3.43 g) was blended ina twin screw extruder at 170° C. for 8 min then extruded.

Example 6

The clay can be ion-exchanged with cations other than Li. Thus, theprocedure of Example 1 can be repeated except that the clay iscation-exchanged with Na.

Example 7

The acid treatment can be applied to clays other than montmorillonite,or to layered non-clay materials. Thus, the procedure of Example 1 canbe repeated except that the acid treatment can be applied to layeredaluminum phosphate.

Example 8

In manner similar to Example 6, the procedure of Example 1 can berepeated except that the acid treatment can be applied to zirconiumphosphate.

Example 9

The method can be used for composites of copolymers of ethylene withother α-olefins or with functionalized monomers. Thus, the procedure ofExample 1 can be repeated except that the olefin is styrene.

Example 10

In manner similar to Example 7, the procedure of Example 1 can berepeated except that the olefin is norbornene.

Example 11

The ethylene pressure can be varied in order to alter the branch contentof the polymer. Thus, the procedure of Example 1 can be repeated exceptthat the ethylene pressure is increased to 3500 kPa.

Example 12

Chlorite was treated with TIBA (2.0 g of 1.0M in hexanes) prior to thedeposition of tetrabenzylzirconium. Chlorite requires lesstetrabenzylzirconium catalyst (10 mg/1.3 g clay) for polymerizationcompared to LiMMT (50 mg/1.3 g clay). The reactor was pressurized with100 psi ethylene. Polymerization at 40° C. for 30 min yielded a whiteshred like material (10.1 g) with 13% clay loading. The activity forthat polymerization is 918 kg/mol/h. The clay layers in the chloriteactivated materials are not exfoliated. The chlorite material did notform any char during the char test but it self-extinguished after 1:28.

Example 13

A 5.7 wt % PE/LiMMT composite made with the eta-3 Ni catalyst by in situpolymerization was also shown to self-extinguish. It self-extinguishedafter 3:51. [not shown in Figures]. To make the composite, catalystsolution (9.6 micromol in 1 g of toluene) was added to a slurry of 200mg of LiMMT in 100 g of toluene. The slurry was placed inside a batchpolymerization reactor. The temperature was equilibrated at 40° C. andethylene (100 psi) was added on demanded for 30 min. The reactionyielded 5.3 g of PE with a clay content of 5.7 wt %.

Example 14

Acid-treated lithium montmorillonite was prepared by stirring asuspension of untreated clay in a solution of Li₂SO₄ and concentratedH₂SO₄ for 5 hours. This material retains its sheet-like structure butthe interlayer association is greatly disrupted, as shown by the absenceof an XRD (001) reflection at 2θ=7°, as shown in FIG. 9.

85 mg Acid-treated lithium montmorillonite was partially dehydrated byheating at 100° C. under a dynamic vacuum (12 hours at ≦10-4 Torr) andthen transferred to a N₂-filled glove box. A dark orange solution of theair-sensitive catalyst, LNi(η³-CH2Ph) whereL=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato(4 mg in 1 g toluene) was mixed with a slurry of 85 mg clay suspended in26 g toluene for 30 mins at room temperature inside a batchpolymerization reactor thermostated at 25° C. The reactor waspressurized with 689 kPa C₂H₄ and polymerization proceeded for 70 mins.The reaction yielded 3.2 g of polyethylene with Mw=1,089,000 g/mol, apolydispersity index of 2.8 and a clay content of 2.6 wt %.

Evidence for nanocomposite formation is shown in the transmissionelectron microscopy (TEM) image of FIG. 10A. Individual clay sheets arevisible in profile as dark lines against the light gray polyethylenebackground.

Example 15

The procedure of Example 14 was repeated except that 500 mg acid-treatedlithium montmorillonite was used. The result was a yield of 4.7 g ofpolyethylene Mw=1,146,000 g/mol, a polydispersity index of 2.7 and aclay content of 10.6 wt %. Evidence for nanocomposite formation is shownin the transmission electron microscopy (TEM) image of FIG. 10B.

Example 16

The procedure of Example 14 was repeated except that 4 g of the solvent,toluene, was replaced with 4 g of 1-hexene, and polymerization proceededfor 30 mins. The reaction yielded 3.6 g of polyethylene with a claycontent of 2.4 wt %. Evidence for nanocomposite formation is shown inthe transmission electron microscopy (TEM) image of FIG. 10C.

The images of FIG. 2 show that most of the clay is exfoliated. Groups ofless than 5 associated, possibly intercalated, clay sheets are alsopresent. High clay dispersion was observed up to 11 wt % loading, and inthe presence of co-monomer.

Example 17

The clay can be cation-exchanged with cations other than Li. Thus, theprocedure of Example 14 can be repeated except that the clay iscation-exchanged with Na.

Example 18

The acid treatment can be applied to clays other than montmorillonite,or to layered non-clay materials. Thus, the procedure of Example 14 canbe repeated except that the acid treatment can be applied to layeredaluminum phosphate.

Example 19

In manner similar to Example 18, the procedure of Example 14 can berepeated except that the acid treatment can be applied to zirconiumphosphate.

Example 20

The structure of the catalyst can be varied via the nature of the donoratoms and the substituents on the ligand L, the initiating group R andthe ancillary ligand S. Thus, the procedure of Example 14 can berepeated except that the late transition metal Pd may be substituted forthe late transition metal Ni.

Example 21

In manner similar to Example 20, the procedure of Example 14 can berepeated except that the late transition metal Pt may be substituted forthe late transition metal Ni.

Example 22

In manner similar to Example 20, the procedure of Example 14 can berepeated except that the late transition metal Fe may be substituted forthe late transition metal Ni.

Example 23

In manner similar to Example 20, the procedure of Example 14 can berepeated except that the late transition metal Co may be substituted forthe late transition metal Ni.

Example 24

The method can be used for composites of homopolymers other thanpolyethylene. Thus, the procedure of Example 14 was repeated except thatthe olefin was propylene and the catalyst was LNi(η¹-CH₂Ph)(PMe₃) whereL=2-methylene-3-(2,6-diisopropylphenylimino)propoxide. A mixture of thecatalyst (8 mg in 1 g toluene) and bis(1,5-cyclooctadiene)nickel (30 mgin 2 g toluene) was added to a slurry of 450 mg clay suspended in 55 gtoluene. The reactor was pressurized with 937 kPa C₃H₆ and thepolymerization proceeded for 180 mins. The reaction yielded 1.4 g of apolypropylene composite with a clay loading of 32%.

Example 25

The method can be used for composites of copolymers of ethylene withother α-olefins or with functionalized monomers. Thus, the procedure ofExample 14 can be repeated except that the olefin is styrene.

Example 26

In manner similar to Example 25, the procedure of Example 14 can berepeated except that the olefin is norbornene.

Example 27

The ethylene pressure can be varied in order to alter the branch contentof the polymer. Thus, the procedure of Example 14 can be repeated exceptthat the ethylene pressure is increased to 3500 kPa.

Example 28

The procedure of Example 14 can be used to make a masterbatch with highclay loading which then can be blended with pure polymer (polyethylene,polypropylene, copolymers of ethylene with other alpha-olefins, etc) tocreate composites with the desired clay loading. Thus, the procedure ofExample 14 can be repeated except that a slurry of 0.25 g clay suspendedin 40 g toluene can be treated with 1 mg of the catalyst of Example 14(in 1 g toluene). The reactor can be pressurized with 689 kPa C₂H₄ andpolymerization can proceed for 4 mins, to yield polyethylene having aclay content of at least 40 wt. %.

Example 29

500 mg of neat second catalyst component trimethylaluminum (TMA) wasadded dropwise to a rapidly stirred suspension of 3 g acid-treatedmontmorillonite in 10 g toluene. The clay was then filtered and washedthree times with fresh toluene to remove unreacted TMA. A portion of theclay (626 mg) was resuspended in 70 g toluene and transferred to a 300mL Parr reactor. 1 g of catalyst solution (16 mg LNi(η³-CH₂Ph) catalystwhereL=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidatoin 3 g toluene) was added, the reactor was sealed and removed from theglove box. After thermal equilibration at 40° C. with stirring, ethylenewas added on demand at 100 psi for 35 minutes. The activity is similarto that of the catalyst supported on unmodified clay, under similarconditions in the same reactor. 5.6 g of material (containing 11.1 wt %clay) was recovered. It appeared fluffier (i.e., less granular) thanmaterials previously produced using clay without TMA modification.

FIG. 11 shows TEM images of an 11.1 wt % clay-polyethylene compositeproduced with TMA-modified clay catalyst. While the clay iswell-distributed in the polymer matrix, it is not highly exfoliated.This may be a consequence of TMA-induced catalyst leaching, resulting inpolymerization other both on and off the surface of the clay. The fluffyappearance of the polymer is consistent with this explanation, since itresembles materials produced by homogeneous acid-activated catalysts.

Example 30

31.1 g Acid-treated lithium montmorillonite was partially dehydrated byheating at 200° C. under a dynamic vacuum (12 hours at ≦10-4 Torr). Theclay was then suspended in toluene (100 g) and transferred, under N₂, toa 2 L autoclave reactor containing 1 L toluene. A solution of thecatalyst, LNi(η³-CH₂Ph) whereL=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato(16 mg in 5 g toluene) was transferred to the burst valve of thereactor. The reactor was thermostatted at 40° C. The catalyst solutionwas pushed into the reactor with ethylene at 1800 kPa, creating theclay-supported catalyst in situ. The polymerization was allowed toproceed isothermally for 30 mins. The reaction yielded 242 gpolyethylene with a clay content of 13.2 wt. %.

Example 31

0.5 g Acid-treated lithium montmorillonite was partially dehydrated byheating at 100° C. under a dynamic vacuum (12 hours at ≦10-4 Torr) andthen transferred to a N₂-filled glove box. A solution of the catalyst,tetrabenzylzirconium (140 mg in 2 g toluene) was mixed with a slurry of2.5 g clay suspended in 80 g toluene for 30 mins at room temperatureinside a batch polymerization reactor thermostated at 55° C. The reactorwas pressurized with 965 kPa C₃H₆ and polymerization was allowed toproceed for 60 mins. The reaction yielded 8.65 g polypropylene with aclay content of 28.9 wt. % and a melting point of 148° C.

Example 32

430 mg Acid-treated lithium montmorillonite was partially dehydrated byheating at 100° C. under a dynamic vacuum (12 hours at ≦10⁴ Torr) andthen transferred to a N₂-filled glove box. A solution of the catalystLNi(η¹-CH₂Ph)PMe₃ where L=3-(2,6-diisopropylphenylimino)-butan-2-one (16mg in 2 g toluene) and Ni(COD)₂ (37 mg in 1.5 g toluene) were mixed witha slurry of 430 mg clay suspended in 40 g toluene for 30 mins at roomtemperature. The clay-supported catalyst was allowed to settle and thesolvent decanted. 60 g fresh toluene and additional Ni(COD)₂ (38 mg in1.5 g toluene) was then added. The catalyst suspension was thentransferred to a batch polymerization reactor and thermostatted at 25°C. The reactor was pressurized with 965 kPa C₃H₆ and polymerizationallowed to proceed for 180 mins. The reaction yielded 1.3 gpolypropylene with a clay content of 33.1 wt. %.

REFERENCES

The following publications are hereby incorporated by reference:

-   1. T. G. Gopakumar, J. A. Lee, M. Kontopoulou and J. S. Parent.    Polymer 43 (2002) 5483-5491.-   2. S. S. Ray and M. Okamoto. Prog. Polym. Sci. 28 (2003) 1539-1641.-   3. K. Weiss, C. Wirth-Pfeifer, M. Hofmann, S. Botzenhardt, H.    Lang, K. Bruning and E. Meichel. J. Mol. Catal. A: Chem.    182/183 (2002) 143-149.-   4. E. G. Howard, R. D. Lipscomb, R. N. MacDonald, B. L.    Glazar, C. W. Tullock and J. W. Collette. Ind. Eng. Chem. Prod. Res.    Dev. 20 (1981) 421-428.-   5. G. G. Hlalky. Chem. Rev. 1000 (2000) 1347-1376.-   6. J. Tudor, L. Willington, D. O'Hare and B. Royan. Chem.    Commun. (1996) 2031-2032.-   7. Y. Suga, Y. Maruyama, E. Isobe, T. Suzuki and F. Shimizu. U.S.    Pat. No. 5,308,811 (1994).-   8. Y. Ishihama, E. Isobe, Y. Maruyama, T. Sagae, Y. Suga and Y.    Uehara. EP Patent 0683180 (1995).-   9. T. Sun and J. M. Garces. Adv. Mater. 14 (2002) 128-130.-   10. J. S. Bergman, H. Chen, E. P. Giannelis, M. G. Thomas and G. W.    Coates. Chem. Commun. (1999) 2179-2180.-   11. Y.-H. Jin, H.-J. Park, S.-S. Im, S.-Y. Kwak and S. Kwak.    Macromol. Rapid Commun. 23 (2002) 135-140.-   12. T. Tang, L. Wei and B. Huang. U.S. Pat. No. 6,649,713 (2003).-   13. J. Heinemann, P. Reichart, R. Thomann and R. Mulhaupt. Macromol.    Rapid Commun. 20 (1999) 423-430.-   14. P. Dubois, M. Alexandre and R. Jerome. Macromol. Symp.    194 (2003) 13-26..-   15. M. Alexandre, P. Dubois, R. Jerome, M. Gareia-Marti, T.    Sun, J. M. Garces, D. M. Millar and A. Kuperman. Patent WO 99/47598    (1999).-   16. H. G. Jeon, H.-T. Jung, S. W. Lee and S. D. Hudson. Polymer    Bull. 41 (1998) 107-113.-   17. A. Usuki, M. Kato, A. Okada and T. Kurauchi. J. Appl. Polym.    Sci. 63 (1997) 137-139.-   18. M. Kawasumi, N. Hasegawa, M. Kato, A. Usuki and A. Okada.    Macromolecules 30 (1997) 6333-6338.-   19. N. Hasegawa, M. Kawasumi, M. Kato, A. Usuki and A. Okada. J.    Appl. Polym. Sci. 67 (1998) 87-92.-   20. D. Kaempfer, R. Thomann and R. Mulhaupt. Polymer 43 (2002)    2909-2916.-   21. P. H. Nam, P. Maiti, M. Okamoto, T. Kotaka, N. Hasegawa and A.    Usuki. Polymer 42 (2001) 9633-9640.-   22. K. H. Wang, M. H. Choi, C. M. Koo, Y. S. Choi and I. J. Chung.    Polymer 42 (2001) 9819-9826.-   23. N. Hasegawa, M. Okamoto, M. Kawasumi, M. Kato, A. Tsukigase    and A. Usuki. Macromol. Mater. Eng. 280/281 (2000) 76-79.-   24. E. Manias, A. Touny, L. Wu, K. Strawhecker, B. Lu and T. C.    Chung. Chem. Mater. 13 (2001) 3516-3523.-   25. M.-S. Hsiao, G.-Y. Chang, S.-Y. Lee and S.-J. Jong. U.S. Pat.    No. 6,838,508 (2005).-   26. Z. M. Wang, H. Nakajima, E. Manias and T. C. Chung.    Macromolecules 36 (2003) 8919-8922.-   27. S.-S. Hou and K. Schmidt-Rohr. Chem. Mater. 15 (2003) 1938-1940.-   28. T. Sun, J. M. Garces and Z. R. Jovanovic. International Patent    Application Publication No. WO 01/30864 (2001).-   29. B. Y. Lee, G. C. Bazan, J. Vela, Z. J. A. Komon and X. Bu. J.    Am. Chem. Soc. 123 (2001) 5323-5353.-   30. Bartholmai, M.; Schartel, B. Polym. Adv. Technol. 2004, 15, 355.-   31. Beyer, G. Plastics Additives & compounding, 2002, 22.-   32. Ray, S. S.; Okamoto, M. Prog. Polym. Sci. 2003, 28, 1539.-   33. Blumstein, A. J. Polym. Sci. 1965, A 3, 2665.-   34. Burnside, S. D.; Giannelis, E. P. Chem. Mater., 1995, 7, 1597.-   35. Giannelis, E. Adv. Mater. 1996, 8, 29.-   36. Lee, J.; Takekoshi, T.; Giannelis, E. Mater. Res. Soc. Symp.    Proc. 1997, 457, 513.-   37. Zanetti, M.; Camino, G.; Reichart, P.; Mulhaupt, R. Macromol.    Rapid Commun. 2001, 22, 176.-   38. Qin, H.; Zhang, S.; Zhao, C.; Feng, M.; Yang, M.; Shu, Z.;    Yang, S. Polym. Degrad. Stab. 2004, 85, 807.-   39. Morgan, A. B.; Harris, R. H., Jr.; Kashiwagi, T.; Chyall, L. J.;    Gilman, J. W. Fire Mater. 2002, 26, 247.-   40. Zhu, J.; Uhl, F. M.; Morgan, A. B.; Wilkie, C. A. Chem. Mater.    2002, 14, 881.-   41. Zhao, C.; Qin, H.; Gong, F.; Feng, M.; Zhang S.; Yang, M. Polym.    Degrad. Stab. 2005, 87, 183.-   42. Gilman, J. W. Appl. Clay Sci. 1999, 15, 31.-   43. Babrauskas, V.; Peacock, R. D. Fire Safety Journal 1992, 18,    255-261.-   44. Gilman, J.; Kashiwagi, T.; Lomakin, S.; Giannelis, E.; Manias,    E.; Lichtenhan J.; Jones, P. Fire Retardancy of Polymers: the Use of    Intumescence. The Royal Society of Chemistry, Cambridge, 1998.-   45. Gilman, J. W.; Jackson, C. L.; Morgan, A. B.; Harris, R., Jr.;    Manias, E.; Giannelis, E. P.; Wuthenow, M.; Hilton, D.;    Phillips, S. H. Chem. Mater. 2000, 12, 1866.-   46. Yang, F.; Yngard, R.; Nelson, G. L. J. Fire Sci. 2005, 23, 209.

Although the present invention has been described in connection with thepreferred embodiments, it is to be understood that modifications andvariations may be utilized without departing from the principles andscope of the invention, as those skilled in the art will readilyunderstand. Accordingly, such modifications may be practiced within thescope of the following claims.

1. A method for forming a flame retardant composite polymer by olefinpolymerization, comprising: treating at least one filler, selected fromthe group consisting of layered silicates and non-silicate compounds;combining said filler with an early or late transition metal firstcatalyst component that becomes activated for olefin polymerization whenin contact with the filler, and contacting an olefin with the activatedcatalyst—filler combination either (a) in the absence of analkylaluminum second catalyst component or (b) in the presence analkylaluminum or an alkylaluniinoxane second catalyst component when thefirst catalyst component is an early transition metal catalyst, wherebyto form an filler-polyolefin composite incorporating platelets of saidfiller, and having flame retardant properties.
 2. The method of claim 1in which said filler is a layered filler.
 3. The method of claim 1 inwhich said filler is clay.
 4. The method of claim 3 in which said clayis chlorite or montmorillonite.
 5. The method of claim 4 in which saidmontmorillonite is treated by acid whereby to partly disrupt its layeredstructure.
 6. The method of claim 1 in which said filler is treated witha Brønsted base or a silylating agent.
 7. The method of claim 1 in whichsaid olefin is a) ethylene, b) propylene or c) a combination of ethyleneand an α-olefin.
 8. The method of claim 1 in which sufficient filler isused to constitute greater than 0.5 weight % of the composite.
 9. Themethod of claim 1 in which sufficient filler is used to constitute atleast 30 weight % of the composite to prepare a high clay-loadedcomposite masterbatch incorporating platelets of said layered filler.10. The method of claim 9 including the step of blending a predeterminedamount of one or more olefinic polymers with said masterbatch to obtaina composite having a desired amount of loading.
 11. The method of claim1 in which said early or late transition metal catalyst is anon-metallocene catalyst.
 12. The method of claim 11 in which saidcatalyst is a nickel complex bearing an α-iminocarboxamidato ligand. 13.The method of claim 12 in which said complex has the general formula I,II, III, IV or V:

wherein: M is Ni, Pt, Pd; A is a a substituted π-allyl, a π-benzyl, asubstituted π-benzyl, benzoyl or picolino ligand; X is N, P or CH; Y isO, CH₂, or S; L is N or P or a structure that is capable of being aneutral two electron donor ligand; L¹ is a neutral monodentate ligandand L² is a monoanionic monodentate ligand, or L¹ and L² taken togetherare a monoanionic bidentate ligand, provided that said monoanionicmonodentate ligand or said monoanionic bidentate ligand is capable ofadding to said olefin; B is a bridge connecting covalently anunsaturated carbon and L; R¹, R², R^(3A) and R^(3B) are the same ordifferent and are each independently hydrogen, hydrocarbyl group, orsubstituted hydrocarbyl bearing functional group; the designation:

is a single or double bond; and R^(3B) is nothing when B is connected toL by a double bond.
 14. The method of claim 12 in which saidα-iminocarboxamidato catalyst is(N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato)Ni(□³-CH₂Ph).15. The method of claim 12 in which said α-iminocarboxamidato ligand isN-phenyl-2-(2,6-dimethylphenylimino)propanamidate.
 16. The method ofclaim 11 in which said catalyst has the formula MR_(x) where M is anearly transition metal, R is an alkyl or substituted alkyl ligand, and xis from 3 to
 6. 17. The method of claim 16 in which the metal componentis selected from titanium, zirconium, hafnium, vanadium, niobium,tantalum, chromium, molybdenum, and tungsten, the alkyl or substitutedalkyl ligand lacks an alpha-hydrogen, and x is
 4. 18. The method ofclaim 17 in which the alkyl or substituted alkyl ligand is selected fromneopentyl, neosilyl, benzyl, and adamantyl groups.
 19. The method ofclaim 16 in which said catalyst is tetrabenzylzirconium.
 20. The methodof claim 1 in which the filler is propylene and the amount of fillerbeing used constitutes at least 30% weight % of the composite to preparea highly clay-loaded composite masterbatch incorporating platelets ofsaid clay.
 21. A flame retardant polymer composite prepared by themethod of treating at least one filler, selected from the groupconsisting of layered silicates and non-silicate compounds, combiningsaid filler with an early or late transition metal first catalystcomponent that becomes activated for olefin polymerization when incontact with the filler, and contacting an olefin with the activatedcatalyst—filler combination either (a) in the absence of analkylaluminum second catalyst component or (b) in the presence analkylaluminum or an alkylaluminoxane second catalyst component when thefirst catalyst component is an early transition metal catalyst, wherebyto form an filler-polyolefin composite incorporating platelets of saidfiller, and having flame retardant properties, wherein the silicate'slayered structure is disrupted and the flame retardant properties are aresult of including the filler.
 22. A flame retardant compositecomprised of at least a polyolefin, a layered filler, selected from thegroup consisting of silicates and non-silicate compounds, and acomponent derived from a complex containing a metal ion and a ligandcontaining a heteroatom, wherein the filler's layered structure isdisrupted and the flame retardant properties are a result of includingthe filler.
 23. A flame retardant composite comprised of at least apolyolefin, a layered filler, selected from the group consisting oflayered compounds other than silicates and silicates, and an organiccompound that can form a radical via pyrolysis or other decompositionprocess, wherein the filler's layered structure is disrupted and theflame retardant properties are a result of including the filler.